The invention relates to a coating device, comprising at least one recipient, which can be evacuated and is intended for receiving a substrate, at least one gas supply device, by means of which at least one gaseous precursor can be introduced into the recipient, and at least one heatable activation element, which has a predeterminable longitudinal extent and is fastened almost immovably in relation to the recipient by means of at least one dedicated mechanical fastening device. The invention also relates to a corresponding coating method.
Coating devices of the type mentioned at the beginning are intended according to the prior art for coating a substrate by means of a hot-wire activated chemical vapor deposition. The deposited layers may, for example, comprise carbon, silicon or germanium. Correspondingly, the gaseous precursors may, for example, comprise methane, monosilane, monogermanium, ammonia or trimethylsilane.
K. Honda, K. Ohdaira and H. Matsumura, Jpn. J. App. Phys., Vol. 47, No. 5, discloses using a coating device of the type mentioned at the beginning for depositing silicon. For this purpose, silane (SiH4) is supplied as a precursor by means of the gas supply device. According to the prior art, the precursor is disassociated and activated at the heated tungsten surface of an activation element, so that a layer of silicon or a layer comprising silicon can be deposited on a substrate.
However, a disadvantage of the cited prior art is that an undesired reaction of the material of the activation element with the precursor takes place, particularly at the colder clamping points of the activation element. For example, the use of a silane compound as a precursor may lead to the formation of silicide phases on the activation element.
The silicide phases occurring during the reaction generally lead to changes in volume of the activation element, are brittle in comparison with the starting material and cannot withstand such great mechanical forces, and they often exhibit a changed electrical resistance. This has the effect that the activation element is often already destroyed after being in operation for a few hours. For example, the activation element may be used under mechanical prestress in the recipient and rupture under the influence of this mechanical prestress. In order to prevent rupturing of the activation element under mechanical prestress, the prior art proposes flushing the clamping points with an inert gas. Although the prior art does show that the service life is extended to a limited extent, this is still insufficient when performing relatively long coating processes or for carrying out a number of shorter coating processes one directly after the other. Furthermore, the inert gas that is used influences the coating process.
The invention is consequently based on the object of extending the service life of an activation element in a coating device for hot-wire activated chemical vapor deposition without disadvantageously influencing the coating process. The object of the invention is also to increase the stability of the process and/or to simplify the control of the process.